[md PATCH 14/26] md/bitmap: protect clearing of ->bitmap by mddev->lock

[NeilBrown <neilb@suse.de>]

This makes it safe to inspect the struct while holding only
the spinlock.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 drivers/md/bitmap.c |    2 ++
 drivers/md/md.h     |    1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1695ee5f3ffc..3424b1915fc4 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1619,7 +1619,9 @@ void bitmap_destroy(struct mddev *mddev)
 		return;
 
 	mutex_lock(&mddev->bitmap_info.mutex);
+	spin_lock(&mddev->lock);
 	mddev->bitmap = NULL; /* disconnect from the md device */
+	spin_unlock(&mddev->lock);
 	mutex_unlock(&mddev->bitmap_info.mutex);
 	if (mddev->thread)
 		mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
diff --git a/drivers/md/md.h b/drivers/md/md.h
index e41559dccdc9..8770308a8052 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -392,6 +392,7 @@ struct mddev {
 	 *   clearing MD_CHANGE_*
 	 *   in_sync - and related safemode and MD_CHANGE changes
 	 *   pers (also protected by reconfig_mutex and pending IO).
+	 *   clearing ->bitmap
 	 */
 	spinlock_t			lock;
 	wait_queue_head_t		sb_wait;	/* for waiting on superblock updates */